How much water do you really need?

Drink water. Drink more water. Drink water before and after you exercise. Sure, I'd heard all of that advice a million times but somehow, when I did my first distance triathlon in the heat of the competition, I forgot all about what I’d read in EatingWell Magazine’s article “Eat to Win” about what to eat and drink while you exercise. I mean, it was sweltering out there. It was a dry hot day on a sunny course. I was doing better than I ever expected. Felt great, in fact. So why stop at the water stops? Why let someone pass me?

hen, as I started to get toward the end of the race, my body slowed down. My mind slowed down. I felt lethargic. I lost five places in the last mile. But after I crossed the finish line, the really weird things started to happen: I couldn't find my bike. Or my car. Or my friends. In fact, I couldn't remember much, to the point where I forgot that I had finished the race and went to start the bike leg again. Finally, a friend said, "You're dehydrated," a fact confirmed later in the medical tent.

The American Council on Exercise (ACE) suggests sipping an additional 17 to 20 ounces of water 2 hours before you exercise. But in 1 hour of exercise, the body can lose more than a quart of water—especially when it’s hot, like it was the day of my race. So it’s important to drink while you’re exercising too: 7 to 10 ounces every 10 to 20 minutes.

More isn’t better: Too much water can make you sick, a condition called hyponatremia where you essentially waterlog your system. So can going too long without replenishing electrolytes, such as sodium. So if you’re working out hard for more than 45 to 60 minutes, you’ll want to choose a sports drink or consume a food that contains some sodium (e.g., pretzels) with your water. (As for eating, check out these 4 natural fuel foods.)

And it’s not always easy to drink on the run, or the ride, so once you finish exercising you’ll want to replenish the fluids you’ve lost by drinking more. ACE suggests weighing yourself before, and after, exercise to see how much “water weight” you’ve lost. You should sip 16 to 24 ounces of fluids for every pound you’re lighter. No scale? Drink until your urine is a pale yellow. (Find out how Olympic athletes like Apolo Ohno fuel their bodies before and after a workout.)

Next time, I'm going to drink ahead.

How much water do you drink? What are your tricks for drinking enough? Tell us what you think below.